/*
 * Copyright (C) 2007 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkArgument;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.util.EnumMap;
import java.util.Iterator;

/**
 * Multiset implementation backed by an {@link EnumMap}.
 *
 * <p>
 * See the Guava User Guide article on
 * <a href= "https://github.com/google/guava/wiki/NewCollectionTypesExplained#multiset">
 * {@code Multiset}</a>.
 *
 * @author Jared Levy
 * @since 2.0
 */
@GwtCompatible(emulated = true)
public final class EnumMultiset<E extends Enum<E>> extends AbstractMapBasedMultiset<E> {
    /** Creates an empty {@code EnumMultiset}. */
    public static <E extends Enum<E>> EnumMultiset<E> create(Class<E> type) {
        return new EnumMultiset<E>(type);
    }

    /**
     * Creates a new {@code EnumMultiset} containing the specified elements.
     *
     * <p>
     * This implementation is highly efficient when {@code elements} is itself a {@link Multiset}.
     *
     * @param elements the elements that the multiset should contain
     * @throws IllegalArgumentException if {@code elements} is empty
     */
    public static <E extends Enum<E>> EnumMultiset<E> create(Iterable<E> elements) {
        Iterator<E> iterator = elements.iterator();
        checkArgument(iterator.hasNext(), "EnumMultiset constructor passed empty Iterable");
        EnumMultiset<E> multiset = new EnumMultiset<E>(iterator.next().getDeclaringClass());
        Iterables.addAll(multiset, elements);
        return multiset;
    }

    /**
     * Returns a new {@code EnumMultiset} instance containing the given elements. Unlike
     * {@link EnumMultiset#create(Iterable)}, this method does not produce an exception on an empty
     * iterable.
     *
     * @since 14.0
     */
    public static <E extends Enum<E>> EnumMultiset<E> create(Iterable<E> elements, Class<E> type) {
        EnumMultiset<E> result = create(type);
        Iterables.addAll(result, elements);
        return result;
    }

    private transient Class<E> type;

    /** Creates an empty {@code EnumMultiset}. */
    private EnumMultiset(Class<E> type) {
        super(WellBehavedMap.wrap(new EnumMap<E, Count>(type)));
        this.type = type;
    }

    @GwtIncompatible // java.io.ObjectOutputStream
    private void writeObject(ObjectOutputStream stream) throws IOException {
        stream.defaultWriteObject();
        stream.writeObject(type);
        Serialization.writeMultiset(this, stream);
    }

    /**
     * @serialData the {@code Class<E>} for the enum type, the number of distinct elements, the
     *             first element, its count, the second element, its count, and so on
     */
    @GwtIncompatible // java.io.ObjectInputStream
    private void readObject(ObjectInputStream stream) throws IOException, ClassNotFoundException {
        stream.defaultReadObject();
        @SuppressWarnings("unchecked") // reading data stored by writeObject
        Class<E> localType = (Class<E>) stream.readObject();
        type = localType;
        setBackingMap(WellBehavedMap.wrap(new EnumMap<E, Count>(type)));
        Serialization.populateMultiset(this, stream);
    }

    @GwtIncompatible // Not needed in emulated source
    private static final long serialVersionUID = 0;
}
